Increasing environmental awareness has moved the laundry business towards colder wash temperatures and shorter automatic washing machine cycles. When conventional laundry detergents are used at cold wash temperatures and in shorter wash times, their cleaning performance is reduced; and their bleaching performance is especially reduced.
The present invention overcomes this problem by formulating a phthalimido peroxy caproic acid (PAP) bleaching system at low pH and low builder levels, which provides a fabric treatment composition having an excellent bleaching efficacy.
In addition, calcium carbonate formation is significantly reduced at the low wash liquor pH, which improves the anti-encrustation profile of the composition. This in turn improves the bleaching performance profile of the composition. Without wishing to be bound by theory, the improved anti-encrustation profile ensures the fabric surface is available to the bleaching system because very little or no encrustatation build up occurs on the fabric surface, so optimal bleaching performance is maintained.
The bleaching performance of this composition is further improved when bleach catalysts are additionally incorporated therein, preferred bleaching catalysts are oxaziridinium-based bleach catalysts, transition metal bleach catalysts and bleaching enzymes. Without wishing to be bound by theory, the stability and efficiency of these bleach catalysts are improved by the low pH of the wash liquor, and increased hardness levels in the wash liquor due to the low builder formulation.
Sodium bicarbonate is an excellent buffer salt to obtain the required low pH profile. However, sodium sesquicarbonate can also be used; and sodium sesquicarbonate provides additional benefits including improved dispensing profile and improved storage stability profile. Without wishing to be bound by theory, the additional benefits observed with sodium sesquicarbonate are due to the very low hydration profile of sodium sesquicarbonate; i.e. sodium sesquicarbonate does not further hydrate beyond its dihydrate.
Formulating with a relatively high reserve alkalinity to pH 6.0 ensures the stability of the low pH profile, providing improved robustness of the bleaching system. In addition, carefully choosing a chelant system that has good binding constants to transition metals at the low pH, protect the bleach system and further improve the robustness of the bleach system.
When other components such as hueing agents and brighteners are also incorporated into the composition, careful choice of these ingredients is needed to ensure they are compatible with the more efficient bleach system. Preferably, oxidation resistant hueing agents and oxidation resistant brighteners are incorporated into the composition.
When first wash lipases are also incorporated into the composition, an excellent dingy cleaning performance is observed.
The low pH profile, and increase in wash liquor free hardness levels due to low builder formulation also improves the colour fidelity profile of the composition. Additional colour fidelity benefits are observed when dye lock components are also incorporated into the composition.
Preferably the composition is a solid laundry detergent composition. However, the composition can also be a bleach additive product.